Semiconductor relaxation oscillator



R. O. ENDRES SEMICONDUCTOR RELAXATION OSCILLATOR Filed Sept. 50, 1949 Pmsf -I www L /f maffia/f 2 Sheets-Shea?l l Jan. 12, 1954 Filed sept. '50, 1949 R. O. ENDRES SEMICONDUCTOR RELAXATION OSCILLATOR 2 Sheets-Sheet 2 BASE VOL TA GE maar@ m m @E Snventor Cttorneg Patented Jan. 12, 1954 SEMICONDUCTOR RELAXATION OSCILLATOR Richard O. Endres, Audubon, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application September 30, 1949, Serial No. 118,905

(Cl. Z50- 36) 16 Claims.

This invention relates generally to relaxation oscillators, and more particularly relates to pulse or saw-tooth wave generators of the type employing a semi-conductor device.

lThe `three-electrode semi-conductor has recently been developed as an amplifier or oscillator. This device, which has been termed a transiston has been disclosed in a series of three letters to the Physical Review by Bardeen and Brattain, Brattain and Bardeen, and Shockley and Pearson which appear on pages 239 to 233 of the July 15, 1948 issue. I'he new amplifier includes a block of a semi-conducting material such as silicon or germanium which is provided with two closely adjacent point electrodes called emitter and collector electrodes in contact with one surface region of the material, and a base electrode which provides a large-area, low-resistance Contact with another surface rem gion of the semi-conducting material. This amplier provides voltage as well as current gain under proper operating conditions and may be considered as a three-terminal network having a common input and output terminal. Thus, the device is effectively a four-terminal network having a common input and output electrode which may, for example, be the base electrode.

1n a copending application or" E. Eberhard, filed January 4., 1949, Serial No. 70,661, entitled Relaxation oscillators, there has been disclosed and claimed a relaxation oscillator which t may be utilized for developing a sav/tooth wave or square-topped pulses. The relaxation oscillator is of the type having a capacitor which is slowly charged by a battery through a resistor and is suddenly discharged. The semi-conductor device is utilized for discharging the capacitor. The voltage across the capacitor determines the point of discharge which is reached when the semieconductor device approaches its regenerative region. At this point a current gain is ob tained so that the capacitor can be discharged very rapidly. This relaxation oscillator may be synchronized by externally applied pulses. Alternatively, the oscillator may be arranged to be quiescent in which case it may be triggered by pulses. Finally, the oscillator may be utilized as a frequency divider. However, it has been found that this type of oscillator is not as stable as desired for some applications. Thus, the oscillater is quite sensitive to variations of its supply voltage and it is therefore not well adapted, for example, for use in an impulse counter.

It is the principal object of the present invention to provide improved relaxation oscillators of the type employing a semi-conductor device.

A further object of the present invention is to provide novel pulse or saw-tooth wave generators including a semi-conductor device which may be arranged as an ocillator, in which case the oscillator may be synchronized by externally applied pulses or may be used as a frequency divider; finally, the generator may be arranged to be normally quiescent and may be triggered by pulses.

Another object of the invention is to provide novel semi-conductor relaxation oscillators which are more stable in operation and which can tolerate greater variations of the operating voltages than previously known relaxation oscillators of the semi-conductor type.

A relaxation oscillator in accordance with the present invention includes a semi-conductor device having a semi-conducting body provided with a base electrode, an emitter electrode and a collector electrode in contact with the body. An inductor is connected between the base electrode and ground and operates without parallel resonance to control the frequency of the oscillator. Furthermore, a resistor is provided between a source of voltage and the collector electrode. The emitter electrode is biased in a conventional manner either by a battery or by self-bias means, as is well known. An oscillator of this type will oscillate at a frequency determined by the: inductance of the inductor as a current controlling device and by the resistive load which the semi-conductor device presents and which determines the decay time of the voltage developed. across the inductor. v

An oscillator of this type may be synchronized. Alternatively, it may be arranged to be normally quiescent. This may be effected by adjusting the supply voltages applied to the electrodes of the device. In that case, the circuit may be triggered by externally applied pulses.

Various modiiications of this basic oscillator circuit will be disclosed hereinafter. Some of them combine the features of the Eberhard oscillator above referred to with the novel relaxation oscillator of the present invention having an inductor in its base lead. Such an oscillator will be considerably more stable than previously known relaxation oscillators of the semi-conductor type because two circuits drive the oscillator simultaneously into the regenerative region. Alternatively; it is feasible to provide a parallel resonant circuit which may be coupled or connected to the base electrode. This arrangement in combination with the Eberhard relaxation oscillator will yield a novel type of relaxation oscillator which may be used as a frequency divider.

conductor, as is well known.

The novel features that are considered characteristic of this invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be uriderstood from the following description when read in connection with the accompanying drawings, in which:

Figure 1 is a circuit diagram of ,a'self-.oscillat-f ing, semi-conductor relaxation oscillator includeing an inductor as the frequency determining element and embodying thepresent invention;

Figure 2 is a graph showing the voltages at the three electrodes of the oscillator of Figure 1;

Figure 3 is a circuit diagram of a relaxation oscillator similar to that of Figure 1 which may either be triggered or synchronized by externally applied pulses in accordance with the invention;

Figure 4. is a circuit diagram of a modified relaxation oscillator in accordance with the invention which further includes an RC network;

Figure 5 is a graph illustrating the voltages at the three electrodes of the oscillator of Figure 4;

Figure 6 is a circuit diagram of a relaxation oscillator provided in accordance with the invention with a parallel resonant circuit and an RC network, the oscillator being suitable as a fre-` quency divider;

Figure 7 is a graph illustrating the voltages at the three electrodes of the oscillator of Figure 6;

Figure 8 is a circuit diagram of a modication of the oscillator of Figure 6, the oscillator including two RC networks;

Figure 9 is a graph illustrating the emitter voltage of the oscillator of Figure 8; and

Figure 10 is a circuit diagram of a further modification of the oscillator of Figure Gembodying the present invention.

Referring now to the drawings, in which like components have been designated by the same reference numerals throughout the figures, and particularly to Figure 1, there is illustrated a relaxation oscillator in accordance with the invention, comprisingy a semi-conductor device. The semi-conductor device includes body I0 of semi-conducting material which may consist, for example, of boron, silicon,'germanium, tellurium or selenium containing a small but suiicient number of atomic impurity centers or lattice imperfections as commonly employed for best results in crystal rectiiers. Germanium is the preferred material for body I0 and may be prepared so as to be an electronic N-type semi- The surface of semi-conducting body I0 may be polished and etched in a conventional manner. It is also feasible to utilize the germanium block from la commercial higheback-voltage germanium rectier, such as the type 1N3fl, in which case furtherV surface treatment may not be required.

Semi-conducting body I0 is provided with emitter electrode II, collector electrode I2 and surfaces thereof in which case they may be Sepa. rated by a distance of from 2 to 5 mils. Base electrode I3 provides a low-resistance, non-rectiying contact with the bulk material of semiconducting body Ic and usually is a large-area electrode.

A comparatively large Areverse bias voltage is normally applied between collector electrode I2 and base electrode I3. Assuming an N-type semiconducting body i0, which is believed to have a P-type 'surface layer, a negative voltage must be applied to collector electrode I2 with respect to base electrode I3.' To this end, there may be provided battery I4 having its positive terminal grounded while its negative terminal is connected to .collector electrode i2 by resistor I5. Battery I4 may be vicy-passed for alternating-frequency currents by bypass capacitor I6. Furthermore,

Y a comparatively small forward bias voltage is norbase electrode I3. Emitter electrode II and collector electrode I2 are usually small-area electrodes and may be point contacts consisting, for example, of tungsten or Phosphor bronze wires .having a diameter of the order of 2 to 5 mils and a pointed tip. However, it is not essential that emitter electrode II and collector electrode I2 are small-area electrodes provided they make rectifying, high-resistance contacts with body I0. Emitter and collector electrodes II and I2 are ordinarily placed closely adjacent to each other entire same surfaceof body Iii orvon opposite mally impressed. between emitter electrode I2 and base electrode I3. Assuming, again, an N-type semi-conducting body IE), which is presumed to have a P-type surface layer, a positive voltage must be applied to emitter electrode II with respect to base electrode I3. To this end, battery IT may be provided having its negative terminal grounded while its positive terminal is connected to emitter electrode II through resistor I8. Battery Il may be by-passed for alternating-free quency currents by capacitor 2Q. Resistor I8 is not required for the operation of the oscillator of Figure 1 bui-Serves to limit the emitter current.

In accordance with the present invention, inductor 22 is connected between base electrode I3 and ground. The device as described will operate as a relaxation oscillator. An output wave which consists of positive pulses may be derived across collector resistor I5. To this end, coupling capacitor v23 which also serves as a blocking capacitor, is connected to the collector electrode i2 and the output may be derived from the output terminals 24, one of which is connected to capacitor 23 while the other one is grounded. To obtain sharper output pulses a differentiating network 25 may be provided including series resistor 2E and shunt capacitor 2l.

The operationV of the oscillator of Figure l will be better understood by reference to Figure 2 wherein curve 3l) indicates the base voltage with respect to time, curve 3i the emitter voltage and curve 32 the collector Voltage, is indicated in Figure 2. Curve 28 shows the base current plotted so that a decrease of the curve indicates an increase of the net current iiowing from ground through inductor 22 to base electrode I3. The oscillator of Figure 1 is biased to a regenerative condition. To this end, the supply voltages -applied by batteries I4 and Il should be properly adjusted and furthermore a high impedance at the oscillatory frequency should be provided between base electrode IS and a fixed potential point such as ground.

Let it now be assumed that the oscillator has reached therpoint in its cycle of oscillation where the regenerative condition prevails. Accordingly, a comparatively heavy current will flow from ground through inductor 22, base electrode I3, collector-electrode I2, resistor I5 and battery I4 back to ground as indicated by curve portion 29. Consequently, the voltage of base electrode I3 will increase in a ynegative direction, as shown by curve portion 33 of curve 39. At the same time, the emitter voltage will increase in a negative direction due to the heavier emitter current,

`particular application,

as shown by curve portion 34 of emitter voltage curve 3|, While the collector voltage increases in a positive direction, as shown bycurve portion 35 of collector voltage curve 32.

The voltage across an inductance such as inductor 22 is proportional to the negative value of the rate of change of the current through the inductance, or, in other Words, to the negative value of the iirst derivative of the current with respect to time. Accordingly, as the rate of change of the base current as indicated by curve portion 29 decreases, the base voltage increases again in a positive direction as indicated by curve portion 35. Eventually, the voltages at the electrodes of the oscillator will change in such a direction that the base current decreases again as indicated by curve portion 29. This abrupt change of the rate of change of the current causes a positive voltage swing across inductor 22 which reaches a positive peak indicated at 31. Due to the decrease of the emitter and collector currents, the emitter voltage approaches the positive voltage of battery Il during this time while the collector voltage approaches the negative voltage of battery I4 as clearly shown in Figure 2.

Finally, the high positive base voltage decays again exponentially at a rate determined by the inductance of inductor 22 and by the resistive load represented by the semi-conductor device,

This resistive load is simply the resistance looking into base electrode I3. The exponential decay of the base voltage is illustrated by curve portion 38 of base voltage curve 30. It will thus be seen that the operation of the oscillator of Figure 1 is controlled essentially by the current flowing through base inductor 22.

Eventually, the emitter and base voltages reach such a value that the region of regeneration is again approached and the next cycle of oscillation starts again in the manner previously described. It will accordingly be seen that the frequency of oscillation is determined solely by the inductance of inductor 22 and by the resistive load presented by the semi-conductor device. Experiments have revealed that this frequency of oscillation is considerably lower than that `which would existY if the oscillator would operate as a sine wave oscillator having a parallel resonant circuit connected to its base electrode. This parallel `resonant circuit includes the inductance of .inductor 22 and the distributed capacitance between base electrode I3 and vground as well as the distributed capacitance of inductor 22.

While it will be understood that the circuit specifications of the relaxation oscillator of Figure `l may vary according t the design for any the follow-ing circuit specications are included, by Way of `example only, as suitable for an output pulse frequency of `100 kc. (kilocycles) ,Resistor I5 l-; ohms 1000 -Resistor I8 do..--

100 Inductor 22 4.5

As pointed out hereinabove, positive pulses, such as shown at 32 in Figure 2, may be derived millihenries-- from output terminals 24. These pulses may be differentiated by network to obtain still Vsharper output pulses.

If desired, the negative portion of the differentiated output pulse `may stantially identical with that of Fig. l. However,`

pulse generators and 4l have been illustrated for developing pulses which may be applied to emitter electrode Il or to base electrode I3. Thus, pulse generator 48 may develop positive pulses as indicated at 42 which may be applied to emitter electrode Il through coupling capacitor 43. Alternatively, negative pulses as shown at 44 which are developed by pulse generator 4I, may be applied across inductor 22.

Pulses 42 or 44 may be synchronizing pulses which may be utilized for triggering the oscillator slightly ahead oi' the time when it would normally reach the regenerative region. Thus, it will be obvious that a negative pulse applied to base electrode I3 during the time the voltage across inductor 22 decays as shown by curve portion 38 of Figure 2 will drive the oscillator into its regenerative region. The same applies if a positive pulse is impressed on its emitter electrode at that time, as will be evident from an inspection of curve BI of Figure 2.

It is also feasible to arrange the oscillator of Figure 3 in such a manner that it is normally quiescent. This may be accomplished by reducing either the collector voltage or the emitter Voltage or both. In that case the circuit will be unable to reach the regenerative region but may be triggered into this region by the application of either positive trigger pulses 42 applied to its emitterl electrode or by impressing negative trigger pulses I44 on its base electrode. It is also feasible to apply a sinusoidal Wave to either emitter electrode II or to base electrode I3 for triggering the oscillator.

The oscillator of Figure 4 combines the features of the oscillator of Figure 1 with that of the Eberhard relaxation oscillator disclosed'in the above referred to application Serial No. 70,661. The oscillator of Figure 4 is substantially identical to that of Figure 1 except that capacitor 45 has been provided which is arranged between collector electrode I2 and ground. Accordingly, as previously pointed out, capacitor 45 will be slowly charged to a negative potential from battery I4 through resistor I5. Eventually, when the voltage across capacitor 45 has reached a predetermined negative valuethe capacitor will be suddenly discharged by the semi-conductor device.

In accordance With the present invention the time constant of the RC network consisting of resistor l5 and capacitor 45 and the inductance of inductor 22 are chosen so that the potentials of the collector and base electrodes will decrease in unison during each cycle of oscillation. This Will insure that the relaxation oscillator reaches the regenerative region as determined by its collector potential and by its base potential simultaneously. This is clearly shown in Figure 5 to which reference is now made.

Curve 46 illustrates the base voltage with respect to time, curve 4l the emitter voltage, and curve 48 the collector voltage. Let it be assumed again that the circuit of Figure 4 has reached that point of its cycle of oscillationy where it-is in a 7 regenerative condition. Accordingly, a large current willilowthrough-inductor22 and will rapidly discharge capacitor 45.v 'The curve portieri npof base voltage curve 4G Vindicates-the voltage ldrop ol thebase voltage ldlliirig that period of time; Curve portion 5| of collector voltagecurve ,48 indicates the rise of ythe collector voltage toward ground potential whicnis caused by the discharge of thene'gative charge'onthe capacitor 545.V V.'Ihe el'lttl" Voltg Will ill'claln ah'egatile dle'# tion, as' indicated by curve portion 52 voffciu-ve 541.

Eventually; the now z`of current through ind'ucto'ry 22 'increases flrst'at a slowratefandthen decreases again. This change they rate .'o'f change of the current flowing throughinductor 22 will cause the base voltage to rise, as shown by curve portion53 of curve 46. At the Sametime, the emitter-voltage will rise, as .indicated by curve portion 54 of curve `4l. The collector voltage, however, Willincrease in a negative direction, as 'shown by curve portion 55, because now capacitor 45 is charged to a negative potential 'from battery I4 through resistor I5. Eventually, the voltage across inductor 22 will again decay, as indicated by curve portion 56. During that periodici time, the emitter voltage remains substantially con starrt lsince there is substantially no emitter cuirrent While the collector voltage continuesto increase in a negative direction indicating the con tinued charging of 'capacitor 45.

The circuit of Figure 4 'is accordingly driven into a regenerative condition simultaneouslysby inductor 22 connected to base electrode I3 and yby the RC lnetwork consisting of resistor I5 and capacitor 45 connected to collector-electrode I 2. During Vthis period of timeboth the-base voltage and the collector voltage decrease in unison until the point of generation is 'reached again. The cycle of operation-then'repeats.

The relaxation oscillator of'Figure 4 has greater e stability than previously known semieconductor relaxation oscillators. l'nv other Words, this circuit can tolerate a V percent change in the voltages applied to emitter electrode II and to collector electrode vl2 without varying the frequency oro'scillation. The base voltage-as indicatedby curve 46 reaches a higherpositive value thanthe base voltage of the oscillator of Figure l. A'saw tooth wave may be derived from output terminals 24 rcoupled to collector velectrode I2. :It is also 'feasible totrigger the oscillator of Figure-4 by 'the application of `positive pulses 432 to emitter electrode i I. These positive pulses may be applied to input-terminals 4c which schematically represent a pulse generator such as shown in'Figure 3. It is also feasible to utilize the oscillator of Figure 4 asia frequency divider. vIn other Words,the frequency-fof input pulses 42 `mayl Ibe* an integral multiple of the free-running frequency of the-oscillator. f

By way of example, for a free-running frequency of kc, the following circuit constants maybe used for-the 'oscillator of Figure fl:

The frequency of pulses 42 may be 100 ltilocycles. An output pulseoi a frequencyof 20-kc..may, then be obtained from either emitterelectrode H, collector electrode I2 or from base electrode i 3.

A further overall improvementin stability may be obtained by utilizing the-oscillator of the type illustrated in Figure 6. This oscillator Vis, provided `with aniRC'network-consisting of resistor I5 andpcapacitorfsll connected tocollector electrode I2. However, in this case a parallel resonant circuit 6o is connected to ybase electrodeiIa. VThe parallel resonant circuit includes inductor 6I and capacitor 6-2 and has one of its terminals' grounded. An intermediate point=63 of inductor 5I isconnected to base electrode I3 in order to match the high impedance `of theparallel resc-y nantcircuit 60 .to the comparatively low impedance of the base electrode.

`The 'relaxation voscillator of `Eigure 6 h'asthe same circuit-elements as the `quench Aoscillator disclosed andclaimed-in a copending application SerialNo. 113262, iiled August-31, .1949, ventitled Semi-Conductor oscillators by Endres and Eberhard.v Y

In the quench frequency oscillator disclosed by Endres and vEberhard the resonant `frequency of the parallel resonant circuit very much higher than the reciproca-lof the time oonstantroi the RC network. In' other words, during'each charge and ldischarge cycle of the RC network 'a large numberofoscillations will occur in the parallel resonant circuit. In accord-ancewith the present invention the time constant of resistor I5 and capacitor .is only slightly larger than'the reciprocal of the vresonant frequency of .parallel resonant circuit/'. Thus, during 'eachch'arge cycle of ca` pacitor 45 there willbe a fev/oscillations of par alici-resonant circuit 60 such as -five orfone oscillation. Howeven `the sinusoidalwave developed inparallel resonant circuit 60 will have a substantiallyconstant amplitude. Y l

Preferably, however, the time constant of resistor I5 and capacitor 45 is'equalto the reciprocal of the resonant frequency of- .parallel'resonant circuit Sil. For a better understanding of the operation of the relaxation oscillator of fFigfure 6, reference is now made to Figure 'Z'illustrate ing the base'voltage curve 65 plotted with respect `to time, the collector voltage Shown byvcu'rvef66 and theemitter voltage shown by curve 61. The circuit'is againbiasedto regeneration and 'is so ,arranged that Ythe base voltage andthe collector voltage go inthe negative'direction at the same time asshown by curves and 66. Y

Letait now beassumed, again, that the circuit approaches the regenerative region. Accordingly, alarge current will fiow-betwecn'the collector and rbase electrodes in rtheV .manner previously de;- scribed and will rapidly discharge capacitor 45 as shownbycurve portion 68 of curve 66. Atthe same ytime the emitter `voltage will decrease rapidly, as shown by curve portion '10. Simultaneously, the basevoltage will rst decrease and upon the current being substantially cut off the base yvoltage will'rapidly increase to a very high `positive value as shown by curve portion 1I. lIt V1s to be understood that curve portion 'II has a tive region is reached again whereupon thenext cycle begins. If the voltage swing rdeveloped acrossparallel resonant circuit 60 is suiclen-tly -g'reatA 'so that -it primarily determines the-free- Arunning frequency cfr-the oscillator, a greater change of the collector bias voltage can be tolerated before instability occurs,

It is again feasible -to synchronize the oscillator of Figure 6 by the application of positive trigger pulses 42 to its emitter electrode II. This circuit l may also be used as a frequency divider and the frequency of the input pulses 42 may, for example, be ten times the free-running frequency of the oscillator. ure '7 where p-ulses42 are shown superimposed on emitter voltage curve 6l. By way of example, for a free-running frequency of kc., the following circuit constants may be used for the oscillator of Figure 6:

Resistor I5 ohms 10,000 Resistor I8 do 500 Capacitor 45 microfarads-- .0066 Inductor 6I millihenries 23 Capacitor 62 -microfarads .013

The portion of inductor 6I above tap 63 may be four times that below the tap. The frequency of pulses 42 may be 100 kc. VThe oscillator will be stable over a 60 percent change of the emitter bias voltage and over a percent change of the I collector `bias voltage. The positive peak voltage ground. Furthermore, resistor I4 may be provided in series with resistor I8, and capacitor 'I3 may be connected to the junction point of the two resistors. The positive terminal of battery I1 is grounded while its negative terminal is connected to resistor I8. The function of resistor 'I4 is to prevent capacitor 'I3 from functioning as an alternating current by-pass capacitor. However,

resistor 'I4 is not essential for the operation of the n oscillator and may, therefore, be omitted.

Preferably, the time constants of RC network I5, and of the RC network I8, 'I3 should be equal. However, it is also feasible to make the time constant of network I8, 'I3 one-half the time constant of RC network I5, 45, that is, half the time between the regenerative pulses ofthe oscillator of Figure 6. In that case the output frequency will be twice that of the oscillator of Figure 6.

The operation of the oscillator of Figure 8 is substantially the same as that of the oscillator of Figure 6. However, the emitter voltage now has the saw-tooth wave shape shown by the curve 'I5 of Figure 9. Thus, when the regenerative portion of the cycle is reached, -the emitter voltage will suddenly decrease, as shown by curve portion 16,

' and will rapidly increase again. This is due to f the suddent discharge of capacitor I3 to a negative potential by the emitter-collector current. Thereupon, capacitor 'I3 is slowly charged in a positive direction through battery II having a small negative potential and resistor I8 as shown by curve portion ll. The input pulses 42 of positive polarity may be impressed through input terminals 40 on emitter electrode II as previously explained. It is also feasible to apply negative input pulses 'i8 on input terminals 80, one of which is coupled to collector electrode I2 through coupling capacitor 8l. Similarly, negative pulses shown in 82 may be applied to input terminals 4I This has been illustrated in Fig-` l@ connected between base electrode I3 and ground. It is to be understood that capacitor 45 may be omitted in the circuit of Figure 8 in which case only a single RC network is connected to the emitter electrode. However, such a circuit would not be as stable as that illustrated in FigureS.

Figure 10 illustrates a relaxation oscillator which is a modification of that of Figure 6. In

this case, parallel resonant circuit 85 is connected in series with resistor I8 between battery I'I and emitter resistor I8. Parallel resonant circuit 85 also tends to stabilize the frequency of the relaxation oscillator. Preferably, the resonant frequencies of circuits and 85 are equal. The oscillator of Figure 10 otherwise operates in the manner of that of Figure 6 previously described.

There have thus been disclosed various semiconductor relaxation oscillators, some of which have a considerably better stability than previously known relaxation oscillators of the semiconductor type. Some of the'oscillators can tolerate appreciable variations of their emitter and collector voltage supplies without changing their frequency of oscillation. The oscillators may be triggered or synchronized. Alternatively, they may be used as frequency dividers in impulse coun-ter circuits.

What is claimed is:

l. A relaxation oscillator including a semicon ductor device having a semi-conducting body, a base electrode, an emitter electrode and collector electrode in contact with said body, a source of potential, means for applying a forward bias potential between said emitter and base electrodes, a resistor connected between one terminal of said source and said collector electrode, a ca" pacitor connected in shunt with said resistor, and an inductor connected between said base electrode and the other terminal of said source, said source being so poled as to apply a reverse bias potential between said collector and base electrodes.

2. A relaxation oscillator including a semiconductor device having a semiconducting body, a base electrode, an emitter electrode and a collector electrode in contact with said body, a source of potential, means for applying a forward bias potential between said emitter and base electrodes, a iirst resistor connected between one terminal of said source and said collector electrode, a capacitor connected in shunt with said i'lrst resistor and source, a second resistor connected between said applying means and said emitter electrode, and an inductor connected between said base electrode and the other terminal of said source, said source being so poled as to apply a reverse bias potential between said collector and base electrodes, the time constant of said capacitor and first resistor and the inductance of said inductor being chosen so that the potentials of said collector and base electrodes I will decrease in unison during a portion of each cycle of oscillation.

l a base electrode, an emitter electrode and a collector electrode in contact with said body, a

source of potential, means for applying a forward bias potential between said emitter and base electrodes, a resistor connected between one terminal of said source and said collector elec` trede, a capacitor connected in shunt with said resistor and source, an impedance element' connected between said applying means and said emitter electrode, an inductor connected between landaise' vi'sairirase electrode and the other terminal ci said source, 'said source being so poledfas to apply a reverse bias'potential between said collector 'and ,base electrodes', and' means: for' applying pulses 'to 'said' emitter electrode.

ILA relaxation oscillator comprising asenti- "conductorY devicehavi'ng" a Ysemi-eonducti'ng body, 'a base electrode, an emitter electrode anda colsource being soipoled as to apply a reverse' bias potential between said collector and base electrodes, acapacitor connected in parallel with said 'source and said resistor, `said capacitor being charged relatively slowly in onedirection by said 'source 'through Asaid resistor and'A being. discharged relatively rapidlyV in the other direction through 'said device, and means for applying a forward `bias potential between said emitter and `base electrodes, the time constant of said resistor 'and capacitor being 'approximately equal to the reciprocal of theresonant frequency of said rescriant circuit.

5. A relaxation oscillator comprising a semiconductor device having a semi-conducting body, a base electrode, an emitter electrode and a collector electrode in Contact with said body, a source o potential, a first resistor connected between a terminal of said source and said collector electrode, a parallel resonant circuity connected to the other terminal of said source, said parallel resonant circuit being coupled to said base electrode, said source being so poled as to apply 4a reverse bias potential between said collector andV base electrodes, a capacitor connected in parallel withA said source and said first resistor, means for applying a forward bias potentialbetween said emitter and base electrodes, and a resistor connected between said means to apply a forward bias and said emitter electrode, the time constant of said first resistor and capacitor being approximately equal to the reciprocal of the resonant frequency of said resonant circuit.

6. A relaxation oscillatorcomprising a semiconductor device having a semi-conducting body a base electrode, an emitter electrode and a collector eleotrode in contact with said body, a source of potential, a rst resistor connected between a. terminal of said source and said collector electrode, a parallel resonant circuit connected to the other terminal of said source, said parallel resonant circuit being coupled to said base electrode, said source being so poled as to apply a reverse bias potential between said collector and base electrodes, a capacitor connected in parallel with said source and said rst resistor, means for applying. a forward bias potential between said emitter and base electrodes, said means including a source of potential and a second resistor connected serially between said emitter and base electrodes, the time constant of said first resistor and capacitor being slightly larger than the reciprocal of the resonant frequency of said resonant. circuit, and means for applying pulses of positive polarity to said emitter electrode, the frequency of said pulses being an integral multiple of said resonant frequency. Y

7. A relaxation oscillator comprising a semiconductor device having a semiconducting body, a base electrode, an emitter electrode and a collector electrode in contact with said body, a

rst lsource of potential,a rst vre'esistc'n; connected betweena terminalv of said1 first source and said collector electrode, aV parallel refsonant circuit connected to the other-terminal of Asaid'first source, saidparallel resonant circuit being coupled" to said'base electrode, said rst source being so' poled as'to apply' a reverse biasV potential between said collector and base electrodes, a second source of potential, a second resistor connected between one terminal of said second 'source and said emitter electrode, the other terminal of said second source being connected to said parallel resonant circuit, said second source being so poled asI to apply a forward' bias potential between said emitter and base electrodes, a capacitor connected in parallel with said second source and said second resistor, the time consta-nt' of said, second resistor and capacitor being of the order of the reciprocal!- of the resonantirequency of said resonant4 circuit.,

8. ArelaXat-ionroscillator comprising a semiconductordevice having a semi-conducting body,

lector electrode, a parallel resonant circuit connected to the other terminal of saidflrst source, said parallel resonant circuit being coupled to said base electrode, said first source being so poled as to apply a, reverse biasy potential between said collector and base electrodes, a first capacitor connected inparallel with said first source and said rst resistor, a second source of potential, a second resistor connected. between one terminal of said second source and said emitterelectrode, theother terminal of saidsecond source being connected to said parallel resonant circuit, said second source being so poled as. to apply a forward bias. potential between said emitter and base electrodesya second capacitor connected invparallel with said second sourcek and said second resistor, the time constant of said first resistor and iirst capacitor being. of the order of the reciprocal of the resonant frequency of said resonant circuit.

9. A relaxation oscillator comprising a semiconductor device having asemi-conducting body,

a base electrode,l an. ernitterelectrode and a collector electrode in contact with said. body, a rst sourcer of potential, a rst resistorconnectedbetween a terminal of said rst source and said collector electrode, a Vparallel resonant circuit connected to the other terminal of said iirst source, said parallel resonant circuit being coupled to` said base electrode, said` first. source being so poled as `to apply a reverse bias potential between said collector and base electrodes, a first capacitor connected in parallel with said first source and said rst resistor, a second source of potential, a second resistor and a third resistor connected serially between oneV terminal of said second vsource and saidyemitte'r electrode, the other terminal of saidy second source being connected to said parallel resonant circuit, said second source beingVv so poled as to apply a forward bias e potential between said emitter and base electrodes, asecond capacitor connected inlparallel with said second source and said second resistor, the time constant of said rst resistor and lirst capacitor being approximately equal to the reciprocal oi the resonant frequency of said resonant circuit.

means are provided for applying trigger pulses to one of said electrodes.

1l. An oscillator as defined in claim 10 wherein the frequency of said trigger pulses is an integral multiple of the resonant frequency of said resonant circuit.

12. An oscillator as defined in claim 10 wherein said pulses are of positive polarity and are applied to said emitter electrode.

13. An oscillator as dei-ined in claim 10 wherein said pulses are of negative polarity and are applied to said base electrode.

14. An oscillator as dened in claim 10 wherein wherein said pulses are of negative polarity and are applied to said collector electrode.

15. A relaxation oscillator comprising a semiconductor device having a semi-conducting body, a base electrode, an emitter electrode and a co1- lector electrode in contact with said body, a

source of potential, a resistor connected between 20 trode, said source being so poled as to apply a 25 2,436,021

reverse bias potential between said collector and base electrodes, a capacitor connected in parallel With said source and said resistor, :means for applying a forward bias potential between said emitter and base electrodes, a resonant circuit, said resonant circuit and said means being connected serially between said emitter electrode and said parallel resonant circuit for stabilizing the operation of said oscillator, the resonant frequencies of said resonant circuits being substantially equal, and the time constant of said resistor and capacitor being of the order of the reciprocal oi' said resonant frequencies.

16. An oscillator as dened in claim 15 wherein means are provided for applying pulses of positive polarity to said emitter electrode.

RICHARD O. ENDRES.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,949,383 Weber Feb. 27, 1934 2,476,323 Rack July 19, 1949 Gross Oct. 25, 1949 

